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Altered aminoacyl-tRNA synthetase complexes in G1-arrested Chinese hamster ovary cells
Abstract:
Aminoacyl-tRNA SYNTHETASE COMPLEXES EXISTING IN Chinese hamster ovary (CHO) cells were shown to undergo alterations as a function of the growth state of the cell. The distribution pattern for 13 particulate postribosomal aminoacyl-tRNA synthetases in 10-30% (w/v) exponential sucrose gradients was determined for the enzymes from CHO cells as they exist under three different culture conditions: exponential growth, G1 arrest induced by isoleucine deficiency, and G1 arrest induced by leucine deficiency. The synthetases specific for the amino acids Arg, Asp, Cys, Gln, His, Lys, Met, Thr, and Val have indistinguishable distribution patterns in all three cell types. However, the synthetases specific for Glu, Pro, Leu, and Ile have a unique distribution of synthetase forms in the G1-arrested cultures and this distribution is independent of whether G1 arrest was induced by isoleucine or leucine deficiency. The distribution of synthetase forms in G1-arrested cells differs in a definite, reproducible manner from the profiles obtained with the exponentially growing cells, and this fact is strong evidence for an in vivo role for the synthetase complexes.
Insights
Aminoacyl-tRNA synthetase complexes in Chinese hamster ovary (CHO) cells change based on cell growth state. Specific synthetases show altered distribution in G1 arrest, suggesting a role in vivo.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Aminoacyl-tRNA synthetases are crucial enzymes for protein synthesis.
- These enzymes can form multi-enzyme complexes.
- The role of these complexes in cellular processes is not fully understood.
Purpose of the Study:
- To investigate alterations in aminoacyl-tRNA synthetase complexes in Chinese hamster ovary (CHO) cells.
- To determine if these alterations correlate with the cell's growth state.
- To explore the in vivo significance of these complexes.
Main Methods:
- Analysis of 13 particulate postribosomal aminoacyl-tRNA synthetases.
- Utilized 10-30% (w/v) exponential sucrose gradients for enzyme distribution analysis.
- Compared enzyme patterns in exponentially growing cells versus G1-arrested cells (induced by isoleucine or leucine deficiency).
Main Results:
- Nine synthetases (Arg, Asp, Cys, Gln, His, Lys, Met, Thr, Val) showed consistent distribution across all conditions.
- Synthetases for Glu, Pro, Leu, and Ile exhibited unique distribution patterns in G1-arrested cells.
- This unique distribution was independent of the specific G1 arrest inducer (isoleucine or leucine deficiency).
Conclusions:
- Aminoacyl-tRNA synthetase complexes undergo significant alterations in their distribution based on cell growth state.
- The observed changes in G1-arrested cells suggest a defined, reproducible role for these complexes in vivo.
- These findings provide strong evidence for the functional importance of aminoacyl-tRNA synthetase complexes beyond basic protein synthesis.